1. Technical Field
The present invention relates to a pressure sensor, a sensor array, a method for manufacturing a sensor array, and a grasping apparatus.
2. Related Art
Diaphragm-type ultrasonic sensor devices have been known in the related art (for example, refer to JP-A-2006-319945).
This type of ultrasonic sensor device includes a semiconductor substrate having an opening, two layers of electrodes on an insulating film formed on the surface of the semiconductor substrate to close the opening, and a PZT ceramic thin film layer (piezoelectric film) interposed between the two layers of electrodes. Then, a membrane which has a diaphragm with a multilayer film structure stacked in a planar manner with respect to the opening and a piezoelectric body configured of the piezoelectric film and the two layers of electrodes is formed. In the ultrasonic sensor device, when a predetermined voltage is applied from the upper and lower electrodes to the PZT ceramic thin film layer, the PZT ceramic thin film layer expands and contracts in its in-plane direction, and accordingly, the diaphragm deflects and vibrates in a direction perpendicular to the plane direction to output ultrasonic waves.
In JP-A-2006-319945, a portion of the PZT ceramic thin film layer is exposed to the outside.
It has been generally known that such an ultrasonic sensor device can be applied to a pressure sensor.
For example, in the case where the pressure sensor is applied to a grasping apparatus which grasps an object, the pressure sensor detects, based on a deflection state of the piezoelectric body of the membrane, pressure when the object is grasped by arms or the like of the grasping apparatus.
In this case, since the object directly contacts the piezoelectric film exposed to the outside, a force is locally applied to the piezoelectric body or diaphragm of the membrane, causing a problem that the piezoelectric body or diaphragm of the membrane is likely to be broken.